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A powerful solar flare that exploded from the surface of the sun this week is the biggest in years, NASA says.

The gigantic flash of light and X-ray radiation unleashed at 3:48 a.m. Tuesday was classified as an X6.9 flare, where X is the biggest of five types of solar flares (10,000 times bigger than A-class flares, which are the smallest), NASA reported. X1 is the smallest X-class flare, and X28 is the biggest that does not overload scientific sensors.

The flare was the biggest of just three X-class flares during the current 11-year solar cycle, which started in January 2008, and was also bigger than the last X-class flare of the previous solar cycle, in December 2006, NASA's space weather website reported.

Although solar flares can affect GPS and communication signals, this one disrupted some radio communication frequencies only briefly.

Blast of plasma only average

Solar flares often coincide with coronal mass ejections (CME) — huge bubbles of plasma containing charged particles and energy that blast toward the Earth. They typically hit the Earth's orbit one to three days after leaving the sun, and can interact with the Earth's atmosphere and magnetic field to generate geomagnetic storms. These can knock out satellites and power grids and create brilliant displays of the aurora borealis or northern lights.

While this week's flare was a giant, the associated CME was "only average," said Michael Hesse, chief of the space weather laboratory at NASA's Goddard Space Flight Center, Wednesday in an email.

He added that both the flare and the CME faced about 60 degrees away from the direct line between the Earth and the sun.

That means it is unlikely to affect the Earth much when it reaches Earth's orbit on Thursday or Friday, though NASA said it "cannot rule out" a glancing blow.

Solar activity such as flares are expected to increase as we move toward the peak of the 11-year solar cycle, which is expected in 2013.